/Engine/Plugins/Runtime/NetworkPredictionExtras/Source/NetworkPredictionExtras/Public/MockRootMotionSimulation.h
The aux state should hold state that does not frequently change. It is otherwise the same as sync state. (note that optimizations for sparse aux storage are not complete yet)
struct FMockRootMotionAuxState
int32
EndTimeMS
TMockRootMotion...
Source